HEAT LOSS OF A TRAPEZOIDAL CAVITY ABSORBER FOR A LINEAR FRESNEL REFLECTING SOLAR CONCENTRATOR

SILVANA FLORES LARSEN; MARTÍN ALTAMIRANO; ALEJANDRO L. HERNÁNDEZ

RENEWABLE ENERGY

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2012 vol. 39 p. 198 - 206

0960-1481

The present paper studies the heat loss of a linear absorber with a trapezoidal cavity and a set of pipes used for a linear Fresnel reflecting solar concentrator. The study includes the measurements on a 1.4m long prototype installed in a laboratory, and its thermal simulation in steady state using EnergyPlus software. Results of the measured vertical temperature variation inside the cavity, the surface interior and exterior wall and window temperatures, the global heat loss at steadystate and the heat loss coefficients, are presented for six different temperatures of the pipes. Measurements revealed a stable thermal gradient in the upper portion of the cavity and a convective zone below it. Around 91% of the heat transferred to outdoors occurs at the bottom transparent window, for a pipe temperature of 200 ºC. The heat loss coefficient per area of absorbing pipes ranged from 3.39 W/m2K to 6.35W/m2K (for 110 °C < Tpipe < 285 °C), and it increased with the increase of Tpipe. Simpler and less time-consuming available free software originally designed for heat transfer in buildings was tested to be a possible replacement of the highly complex CFD software commonly used to simulate the steady state heat loss of the absorber. The experimental and predicted data sets were found to be in good agreement.